Photographic silver halide diffusion transfer process



3 000,736 PHOTOGRAPHIC SII NER HALIDE DiFFUSl'ON TRANSFER PROCESS Richard W. Karlson, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Mar. 31, 1958, Ser. No. 724,815 8 Claims. (Cl. 96-29) This invention relates to a photographic process of the silver halide diffusion transfer type wherein undeveloped silver halide of an emulsion layer is transfererd as a silver complex imagewise by imbibition to a silver precipitating or nucleating layer generally to form a positive image therein.

As is known in the art, this type of process can be carried out by developing an exposed emulsion layer with a developing solution containing a silver halide solvent after which the emulsion layer is placed into contact with a second element carrying a silver precipitating layer to cause the undeveloped silver halide to transfer imagewise as a silver complex to the second element and form an image thereon.

The process has also been carried out utilizing a multilayer element such as one carrying on a support two gelatin layers of different solubility, for example, the layer next to the support containing a silver precipitating agent and being harder than the outer gelatin layer which is a gelatin emulsion layer containing silver halide. After exposure of the element, development is carried out with the silver halide solvent'containing developer to obtain a silver positive in the hardened gelatin silver precipitating layer, after which the emulsion layer containing the negative silver image is washed Off, leaving the positive silver image on the support.

In a similar silver halide diffusion transfer process described in Yackel et al. U.S. patent application Serial No. 586,705, filed May 23, 1956, a multilayer element is utilized comprising a silver precipitating stratum on a support and over this-stratum a silver halide emulsion in which the silver halide is uniformly dispersed in an alkalisoluble, acid-insoluble carboxylated cellulose derivative such as cellulose ether phthalate. After exposure of this multilayer element to a subject and development with a developer composition containing a silver halide solvent, the undeveloped silver halide transfers as a soluble complex to the silver precipitating stratum and thereafter the emulsion layer containing the original negative silver image is washed ofi leaving an argental (silver-containing) image on the support.

The silver halide diffusion transfer processes such as described above have a common disadvantage; they tend to produce argental images which are brown in color rather than being neutrally toned as is desired. To alleviate this condition it has previously been proposed to carry out the diffusion transfer processes in the presence of organic compounds such as sulfur-containing heterocyclic compounds which cause the formation of neutrally toned images.

I have discovered that if the silver halide diffusion transfer processes are carried out in the presence of certain nitroindazoles a pronounced improvement in tone, i.e., darkening of the argental images, is obtained. Nitroindazoles have previously been recommended for use in photographic systems as agents for the inhibition of fog. However, no distinction appears to have previously been made between the various indazoles or nitroindazoles as regards ability to affect the image tone of silver images, particularly in silver halide diiiusion transfer processes. That is, I have found that only 5 -n-itroindazole, 6-nitroindazole and 5,6-dinitroindazole are eifective in producing black-toned argental images in diffusion transfer processes when used in emulsions or developer solutions, whereas the following indazoles and related benzimidazoles are completely inelfective as toning agents:

1,3-diphenyl-5-nitroindazole 4-chloro-4-nitroindazole 4-methoxy-5-nitroindazole 7 -nitroindazole S-aminoindazole S-hydroxyindazole 3-chloroindazole 3 -ind azolone Benzimidazole 6-nitrobenzimidazole Z-mercapto-S-nitrobenzimidazole The primary object of my invention, therefore, is to provide means for the use of the three mentioned nitroindazoles in silver halide diffusion transfer processes to efiect improvement in tone of the argental images. Other objects of my invention will become apparent from the following description.

The objects of my invention are accomplished by incorporating the nitroindazoles in developer compositions, emulsion layers, silver precipitating layers or other layers of sensitive elements used in the diffusion transfer processes and using such developers and elements in diffusion transfer processes.

The folliwing examples will serve to illustrate my invention:

Example 1 To 183 grams of silver chloride emulsion containing 0.05 mole of silver halide were added 50 cc. of 4% aqueous gelatin solution, 16 cc. of water, 20 cc. of 0.75% aqueous S-nitroindazole solution, 10 cc. of 7.5% aqueous saponin solution and 0.76 cc. of 20% formaldehyde solution. This emulsion was coatedon a light-weight photographic paper at 500 square feet per mole of silver halide. The coating was exposed, treated with the following developer solution and squeezed into contact with the following receiving sheet in a commercially available machine designed for the silver halide diffusion transfer process. The emulsion-coated paper was stripped from the receiving sheet thirty seconds after the sandwich emerged from the machine. The positive image obtained on the receiving sheet had a dark brown-black color as compared to a greenish-brown color when the S-nitroindazole was omitted from the control emulsion:

Developer: Grams Sodium sulfite, anhydrous 73 1-phenyl-3-pyrazolidone 0.25 Hydroquinone 7 Sodium hydroxide 7 Na S O .5H O 4 Water to 1 liter.

Receiving sheet: A solution, 2800 g., containing: 4% gelatin, 0.00135 mole ZnS, 0.000135 mole Zn(NO 18 g. Na SO 18 g. Na S O -5H O, cc. 7.5% saponin,

16 cc. 20% formaldehyde, was coated on a single weight photographic paper at 11 g./ft.

Example 2 An emulsion was prepared in the manner of Example 1 except using 10 cc. of 1% potassium bromide and 10 cc. of 1% S-nitroindazole in place of the 20 cc. of 0.75% S-nitroindazole. The emulsion was coated and tested as described in Example 1 producing on the receiving sheet a very black image whereas the image tone was greenish-brown when the control emulsion contained only the potassium bromide and no S-nitroindazole.

Example 3 An emulsion was prepared in the manner of Example 1, using 10 cc. of 1% 3-methylbenzothiazolium methyl sulfate plus 10 cc. of 1% S-nitroindazole in place of the 20 cc. of 0.75% S-nitroindazole. When coated and tested as described in Example 1, this produced a very black image, whereas with just the benzothiazolium salt, the image was reddish-brown, and when both the B-methylbenzothiazolium salt and the S-nitroindazole were omitted, the image was greenish-brown.

Example 4 This example is representative of methods for employing the eifective indazoles for producing dark images in the processes of the Yackel et al. U.S. patent application Serial No. 586,705, filed May 23, 1956, which processes employ an element having a silver halide emulsion containing an alkali-soluble, acid-insoluble carboxylated cellulose derivative vehicle, such as a phthalate of ethyl cellulose or of cellulose acetate, coated upon a silver precipitating layer, and the element after exposure is processed with a developer solution containing silver halide developing agent and silver halide solvent in the presence of one or more of the three mentioned nitroindazoles to form an argental image in the silver precipitating layer after which the emulsion layer is washed oil of the silver precipitating layer.

The sensitive element may be prepared by taking 170 cc. of a washed chlorobromide emulsion containing 0.03 mole silver halide, approximately 0.6 g. gelatin, and 87 cc. of a 6% solution of the ammonium salt of cellulose ether phthalate, and adding 10 cc. of 0.46% aqueous nitroindazole solution. This preparation is then coated on a zinc sulfide silver precipitating layer prepared as described in Example 1 of the Yackel et al. invention above by the reaction of sodium sulfide with zinc nitrate.

The resulting element was then exposed to a subject and developed for 60 seconds at 68 F. in a developer of the following composition:

Grams Monomethyl-paminophenol 4.6 Hydroquinone 10.8 Sodium carbonate, monohydrate 80.0 Sodium sulfite, des 50.0 Potassium bromide 1.0

S-methylbenzotriazole 0.08

Meta boric acid 1.5 Sodium tetraphosphate 4.0 Sodium hydroxide 12.0

Sodium thiosulfate (pentahydrate) 23.4 Water to 1 liter.

A coating was prepared and processed in the manner of Example 4, using 1.53 g. of 5,6-dinitroindaz0le per mole of silver in the emulsion in place of S-nitroindazole. In this case, the positive image had a brown-black tone.

Example 6 A coating was prepared in the manner of Example 4, using 1.53 g. of 6-nitroindazole per silver mole in the emulsion in place of S-nitroindazole. In this case, the image was blue-black as in Example 4.

The three mentioned nitroindazoles can be employed in a similar manner in conjunction with the other procedures and elements described in the mentioned invention of Yackel et al.

Example 7 When the process of Example 4 was carried out with 7-nitroindazole in place of 5-nitroindazole, the silver image obtained in the positive print was reddish-brown in color.

Example 8 The sensitive element described in Example 4 was processed as described except using the following developing solution:

Grams l-phenyl-3-pyrazolidone 0.4 Hydroquinone 5.5 Sodium sulfite, des 25.0 Sodium carbonate, monohydrate 32.0 Potassium bromide 0.25 Hypo 10.0 l-B-phenethylquinolinium bromide 0.4

Water to 1 liter. Omission of the quaternary ammonium salt from the solution yields a warmer toned image.

Example 9 The sensitive element described in Example 4 was processed as described except using the following developing solution:

Water to 1 liter.

Omission of the quaternary ammonium salt from the solution yields a warmer toned image.

Example 10 The sensitive element of Example 4 was used having the cellulosic emulsion coated upon the zinc sulfide precipitating layer, except that the S-nitroindazole was ormtted from the emulsion. Processing was carried out as described in Example 4 but using the following developer solution:

Grams Monomethyl-p-aminophenol sulfate 2.0 Hydroquinon 5.0 Sodium sulfite, des 25.0 Sodium carbonate, monohydrate 30.0 Hypo 10.0 5 -nitroindazol 0. 1

3,6,9,12,15,18,21,24 octaoxahexacosane 1,26-bis (5-ethyl-Z-methylpyridiniummethane sulfonate) 0.2 Water to 1 liter.

Omission of either the S-nitroindazole or the quaternary ammonium salt from the solution yields a warmer toned image.

Example 11 The following developer solution is also suitable for producing neutral toned images in the silver halide diifusion transfer processes such as described in Example Water to 1 liter.

Omission of 5-nitroindazole from the solution yields a yellowish-brown image.

In the silver halide diffusion transfer process employing the mentioned nitroindazoles the silver precipitating layer in which the argental image is formed may contain as silver precipitating agents sulfides, selenides, polysulfides, polyselenides, thiourea, mercaptans, stannous halides, heavy metals and heavy metal salts, and fogged silver halide. Heavy metal sulfides such as lead, silver, zinc, antimony, cadmium and bismuth sulfides are useful, particularly the sulfides of lead and zinc alone or in admixture, or complex salts of these with thioacetamide, dithiooxamide, or dithio-biuret. The heavy metals include silver, go-ld, platinum, palladium and mercury preferably in the colloidal form. The noble metals are particularly eflicacious.

The silver precipitating agents may be applied directly to a support such as paper, or to suitably subbed cellulose derivative supports and synthetic polymer supports from solutions or dispersions of the silver precipitating agents in a colloid vehicle such as gelatin. The colloid vehicle of the silver precipitating layer of the invention of Yackel et al. is necessarily insoluble in the solution used for removing the carboxylated cellulose derivative emulsion layer in the final stage of the process. If gelatin is used, it should be hardened.

When the nitro indazoles are employed in the invention of Yackel et al., they may be employed in any of the hydrophilic layers of the sensitive element. In such elements the silver halide emulsion can be applied directly over the silver precipitating layer, but preferably a thin layer of one of the alkali-soluble carboxylated cellulose derivatives, e.g., a dibasic acid ester of cellulose ethyl ether is first applied followed by the emulsion layer. This thin layer is not absolutely essential; however, it has been found to facilitate the clean removal of the emulsion from the silver precipitating layer.

The silver halide component of the mentioned emulsions is not especially critical and can include various silver halides and mixtures of silver halides such as silver bromoiodide, silver chloride or silver bromide optically sensitized in the usual manner. The emulsions may be developing-out emulsions designed for development to negative images in which case the image obtained in the silver precipitating layer is a positive with respect to the original subject. If desired, the emulsion can be of the direct positive type with the result that the silver image developed in the emulsion is a positive and the image in the silver precipitating layer a negative in respect to the original subject. The procedures of Leermakers U.S. Patent 2,184,013 and Kendall et al. U.S. Patent 2,541,472 are useful in conferring the direct positive characteristics to the emulsion.

The silver halide developing solution used for initiating development of the exposed sensitive elements described, in the presence of the mentioned nitroindazoles, is not especially critical and can be of the conventional type used for developing films or papers with the exception that a silver halide solvent such as hypo, sodium thiocyante or ammonia is present in the quantity required to form the soluble silver precipitating layer. Silver halide develop ing agents useful in the developing solution include hydroquinone, monomethyl-p-aminophenol sulfate, aminophenols, halogenated hydroquinones, toluquinone, p-hydroxyphenyl aminoacetic acid, 3-pyrazolidone developing agents such as l-phenyl-3-pyrazolidone and mixtures of these developing agents. Useful developer compositions containing combinations of 3-pyrazolidone silver halide developing agents with weak developing agents such as ascorbic acid are disclosed in U.S. Patents 2,688,549, 2,691,589, 2,688,548, 2,685,515, 2,685,516 and 2,751,300.

The silver halide developing agent may be present in the emulsion layer or developing solution. In the former case it is preferred to use a substantially non-diifusing developing agent such as the dihydroxy diphenyls e.g. 3,4-dihydroxydiphenyl in the emulsion layer. The nitroindazoles may be used in the emulsion layer in quantities of about 0.5 to 4.0 gram per mole of silver halide. When the nitroindazoles are employed in the developer solution, about 0.1 to 2.0 grams per liter are satisfactory.

Other compounds which have been found to appreciably darken the silver images when employed in the developer compositions in silver halide diffusion transfer processes are the following:

N-methyl-2-mercaptobenzarnide 2-mercaptobenzamide S-methyl-benzothiazolium methyl sulfate 3-methyl-benzothiazolium iodide S-methyl-benzothiazolium perchlorate N,N-dimethyl-2,2'-dithiobenzamide NI,N'-dimethyl-2,2-dithioformanilide These compounds may be used in emulsion layers employed in silver halide ditfusion transfer processes alone or in conjunction with other compounds such as the nitroindazoles as described in Example 3 above or in combination with 2-mercapto-5-phenyl-l-oxa-3,5-diazole.

What I claim is:

1. A method of forming a photographic image which comprises exposing to a subject an element including a support, a silver precipitating stratum on the support, and adhered to said stratum a light-sensitive emulsion layer containing silver halide uniformly dispersed in an alkalisoluble acid-insoluble dibasic acid ester of a member of the class consisting of cellulose ethyl ether and cellulose acetate, developing a latent image in the emulsion layer with a silver halide developing solution containing a silver halide developing agent and a silver halide solvent in contiguity with a member of the class consisting of S-nitroindazole, 6-nitroindazole and 5,6-dinitroindazole to form a silver image and imagewise distribution of a soluble silver complex in the emulsion layer, allowing a portion of said silver complex to diffuse imagewise to said silver precipitating stratum and the silver of said portion of silver complex to be precipitated in said stratum as a silver image of improved tone, and removing the emulsion layer from said stratum.

2. A method of forming a photographic image which comprises exposing to a subject an element including a support, a silver precipitating stratum 0n the support, and adhered to said stratum a light-sensitive emulsion layer containing silver halide uniformly dispersed in an alkalisoluble acid-insoluble phthalate of a member of the class consisting of ethyl cellulose and cellulose acetate, developing a latent image in the emulsion layer with a silver halide developing solution containing a silver halide developing agent and a silver halide solvent in contiguity with a member of the class consisting of S-nitroindazole, 6-nitroindazole and 5,6-dinitroindazole to form a silver image and an imagewise distribution of a soluble silver complex in the emulsion layer, allowing a portion of said silver complex to diffuse imagewise to said silver precipitating stratum and the silver of said portion of silver complex to be precipitated in said stratum as a silver image of improved tone, and removing the emulsion layer from said stratum.

3. In a process for the production of photographic images in which an exposed silver halide emulsion layer is developed to produce a silver image and the residual undeveloped silver halide is caused to diffuse imagewise to a receiving stratum by means of a silver halide solvent, and an argental image is formed therein by interaction of said diffused silver halide and a silver precipitating agent, the improvement in which said interaction takes place in association with an additional member, of the class consisting of S-nitroindazole, 6-nitroindazole and 5,6-dinitroindazole to improve the tone of said argental image.

4. In a process for the production of photographic images in which an exposed silver halide emulsion layer is developed to produce a silver image andthe residual undeveloped silver halide is caused to diffuse imagewise to a receiving stratum by means of a silver halide solvent, and an argental image is formed therein by interaction of said diffused silver halide and a silver precipitation agent, the improvement in which said interaction takes place in association with S-nitroindazole to improve the tone of said argental image.

5. In a process for the production of photographic images in which an exposed silver halide emulsion layer is developed to produce a silver image and the residual undeveloped silver halide is caused to diffuse imagewise to a receiving stratum by means of a silver halide solvent, and an argental image is formed therein by interaction of said diffused silver halide and a silver precipitating agent, the improvement in which said interaction takes place in association with 6-nitroindazole to improve the tone of said argental image.

6. In a process for the production of photographic images in which an exposed silver halide emulsion layer is developed to produce a silver image and the residual undeveloped silver halide is caused to diffuse imagewise to a receiving stratum by means of a silver halide solvent,

and an argental image is formed therein by interaction of said diffused silver halide and a silver precipitating agent,- the improvement in which said interaction takes place in association with 5,6-dinitroindazole to improve the tone of said argental image.

7. In a process for the production of photographic images in which an exposed silver halide emulsion layer is developed to produce a silver image and the residual undeveloped silver halide is caused to diffuse imagewise to a receiving stratum by means of a silver halide solvent, and an argental image is formed therein by interaction of said diffused silver halide and a silver precipitating agent, the improvement in which said interaction takes place in association with an additional member of the class consisting of S-nitroindazole, 6-nitroindazole and 5,6-dinitroindazole in combination with a 3-rnethyl benzothiazolium salt, to improve the tone of said argental image. v

8. In a process for the production of photographic images in which an exposed silver halide emulsion layer is developed to produce a silver image and the residual undeveloped silver halide is caused to diffuse imagewise to a receiving stratum by means of a silver halide solvent, and an argental image is formed therein by interaction of said diffused silver halide and a silver precipitating agent, the improvement in which said interaction takes place in association with S-nitroindazole and 3-methyl benzothiazolium sulfate, to improve the tone of said argental image.

References Qited in the file of this patent UNITED STATES PATENTS 2,496,940 Hanson et al Feb. 7, 1950 2,497,917 Stauffer Feb. 21, 1950 2,704,721 Land Mar. 22, 1955 OTHER REFERENCES Mees: The Theory of the Photographic Process, Macmillan, N.Y., 1942, page 460. 

1. A METHOD OF FORMING A PHOTOGRAPHIC IMAGE WHICH COMPRISES EXPOSING TO A SUBJECT AN ELEMENT INCLUDING A SUPPORT, A SILVER PRECIPITATING STRATUM ON THE SUPPORT, AND ADHERED TO SAID STRATUM A LIGHT-SENSITIVE EMULSION LAYER CONTAINING SILVER HALIDEUNIFORMLY DISPERED IN AN ALKALISOLUBLE ACID-INSOLUBLE DIBASIC ACID ESTER OF A MEMBER OF THE CLASS CONSISTING OF CELLULOSE ETHYL AND CELLULOSE ACERATE, DEVELOPING A LATENT IMAGE IN THE EMULSION LAYER WITH A SILVER HALIDE DEVELOPING SOLUTION CONTAINING A SILVER HALIDE DEVELOPING AGENT AND A SILVER HALIDE SOLVENT IN CONTIGUITY WITH A MEMBER OF THE CLASS, CONSISTING OF 5-NITROINDAZOLE, 6-NITROINDAZOLE AND 5,6-DINITTRONINDAZOLE TO FORM A SILVER IMAGE AND IMAGEWISE DISTRIBUTION OF A SOLUBLE SILVER COMPLEX IN THE EMULSION LAYER, ALLOWING A PORTION OF SAID SILVER COMPLEX TO DIFFUSE IMAGEWISE TO SAID SILVERPRECIPITATING STRATUM AND THE SILVER OF SAID PORTION OF SILVER COMPLEX TO BE PRECIPITATED IN SAID STRATUM AS A SILVER IMAGE IF IMPROVED TONE, AND REMOVING THE EMULSION LAYER FROM SAID STRATUM. 